This toddler had a chronic history of thickening of the fingernails and toenails associated with multiple keratotic papules and plaques on the palms, soles, and knees. She also had chronic whitish discoloration of the left tip of her tongue. Through diligent paring and cutting of the nails in conjunction with use of Carmol 20 percent at night, there has been significant improvement in the appearance of the hyperkeratotic lesions. Carmol 40 percent , unfortunately, was too irritating. Tazorotene gel 0.1 percent was recently added for nightly use. Application of moleskin around the margins of keratotic plaques and papules was also suggested to relieve discomfort associated with weight-bearing. No one in the family had similar problems. Pachyonychia congenita (PC) type I (Jadossohn-Lewandowsky syndrome) is an autosomal dominant disorder characterized by subungual hyperkeratosis, palmoplantar calluses over the pressure points of the soles, and benign oral leukokeratosis. The calluses are often tender, and blisters may form near the calluses. Patients may also have follicular keratosis, especially on the knees and elbows, hyperhidrosis, and paronychial infections. PC type II (Jackson-Lawler or Jackson-Sertolli syndrome) is characterized by the presence of additional features, including multiple epidermal cysts, steatocystoma multiplex, natal teeth, wooly scalp hair (pili torti), and bushy eyebrows. Compared to PC type I, PC type II has a lower frequency of oral leukokeratosis and often milder hyperkeratosis. PC type I is caused by mutations in keratins 16 or 6a, while PC type II is caused by mutations in keratins 17 or 6b. Other variants of PC include PC type III (Schafer-Branauer syndrome), which is like PC type I with the addition of corneal leukokeratosis, and PC type IV (PC tarda), which has a later onset and may have areas of hyperpigmentation.
The histology of oral lesions show features of white sponge nevus with epithelial thickening and extensive intracellular vacuolization and without dyskeratosis. Blisters, which may occur around the plantar calluses, show separation in the upper stratum spinosum. Although they are sometimes referred to as friction blisters, they do not show areas of necrosis, which are seen in friction blisters. Nail bed biopsies show hyperkeratosis and, similar to normal nail beds, an absent granular layer.
Treatment for PC involves nail management and attempts at clearing or thinning hyperkeratotic lesions. Avulsion of nails or attempts to destroy the nail matrix may be ineffective in the long term. Occlusion of nails with a keratolytic ointment followed by vigorous paring is the most effective therapy. Palmoplantar keratoderma is best treated with a urea- or lactic acid-based keratolytics. Hyperkeratotic papules and oral leukokeratosis may be cleared with oral retinoids in selected cases.
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